Vapor pressure barriers for lead acid batteries for improved water loss performance, separators, systems, and methods of manufacture and use thereof

ABSTRACT

New or improved lead acid batteries with vapor pressure barriers and/or improved battery separators, as well as systems, vehicles, and/or methods of manufacture and/or use thereof are disclosed herein. In at least select embodiments, the instant disclosure provides new or improved lead acid batteries with a vapor pressure barrier. In at least select embodiments, the instant disclosure provides new or improved lead acid battery vapor pressure barriers along with new or improved battery separators, and/or methods of manufacture and/or use thereof. In at least select embodiments, the instant disclosure provides a new or improved lead acid battery with a vapor pressure barrier that reduces the water loss from the battery. In at least select embodiments, a method of reducing the water loss of a lead acid battery may include providing a vapor pressure barrier, such as a layer of oil, inside the lead acid battery along with an improved battery separator.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.15/054,821, filed Feb. 26, 2016, which claims priority to and thebenefit of co-pending U.S. Provisional Patent Application No.62/121,112, filed Feb. 26, 2015, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The instant disclosure or invention is directed to new or improved leadacid batteries and components therefor, vapor pressure barriers,separators, systems, vehicles, and/or related methods of productionand/or use thereof, and to various vapor pressure barriers and/orsystems of combinations of vapor pressure barriers and separators foruse in a lead acid battery, and to batteries and/or vehicles includingsuch vapor pressure barriers, systems or combinations. In at leastselect embodiments, the instant disclosure or invention is directedtoward a new or improved vapor pressure barrier or barriers, sometimesin conjunction with improved battery separators, for lead acid batteriesand related products, devices or vehicles including such batteries,and/or methods for creating such vapor pressure barriers and/or batteryseparators. In at least select embodiments, the instant disclosure orinvention relates to new or improved lead acid batteries and vehicles,and/or methods of manufacture and/or use thereof for enhancing the waterloss performance of the lead acid battery, which battery may be in aparticular system, device or vehicle.

BACKGROUND OF THE INVENTION

Lead acid batteries have evolved, over time, as the demands for a sourceof mobile electric power have grown. There are two main types of leadacid batteries: flooded lead acid batteries and VRLA (valve regulatedlead acid) batteries. The instant disclosure may be particularly usefulfor flooded batteries which are commonly used all over the world. Anewer type of flooded lead acid battery is an EFB battery, or anenhanced flooded battery. For example, the new, ever growingrequirements for Stop Start car technology (or Idle Stp Start (ISS))demands a better battery which may be the “enhanced” flooded battery, orEFB. Deep cycle batteries used for various industrial applications,mining equipment, golf cars, and other applications, particularly thosewhere periodic overcharge is required, and stationary applicationsrequiring constant overcharge, may also benefit from reduced water losstechnologies. Such systems, and other systems, will see a reduction inrequired maintenance, less frequent watering required, and/or longerservice life, even in cases of irregular maintenance schedules.

Water loss in lead acid batteries is a known problem and may occur formany different reasons. For example, water loss (reduced level ofelectrolyte due to reduced quantity of water in the electrolyte) mayoccur in lead acid batteries as the overvoltage of hydrogen is exceededat the electrodes. This may be typical and may occur to some extent asthe electrochemical mechanism dictates. The effects of water loss may beamplified in climates with sustained high temperature. Water loss hasbeen identified as a major contributor to at least the followingcritical failure modes in lead acid batteries: plate dehydration, whichmay lead to battery failure; dryout in a sealed VRLA battery, which maylead to potential thermal runaway; negative plate sulfation, which maylead to reduced charge acceptance and/or reduced cycle life; and/orincreased specific gravity of electrolyte, which may lead to negativeplate sulfation and/or positive grid corrosion.

Water loss in a lead acid battery can be seen through: reduced level ofelectrolyte leading to dryout, exposing welds, plates and connections tocorrosion and causing early failure; increasing electrolyte acidconcentration, reduced capacity, negative plate sulfation, positive gridcorrosion leading to early failure; and/or outgassing of H₂ and O₂gases, possibly creating an explosion and handling hazard and requiringventing. As such, reducing water loss in lead acid batteries may helpeliminate: plate dehydration leading to early capacity loss andshortened life; negative plate sulfation, reducing life; and/or positivegrid corrosion, reducing performance by robbing CCA (cold crankingamperage) and capacity and life. Water loss from lead acid batteries maybe mainly due to electrolysis and subsequent gassing of hydrogen andoxygen, which may be more apparent in high temperature climates orapplications.

EFBs may suffer from any of these water loss scenarios, includingevaporation and electrolysis of water. Water loss, whether throughevaporation and/or electrolysis, is commonly known to lower theperformance and/or life of the EFB. As such, many methods have beendeveloped to combat this drawback, including VRLA/AGM type batteries.However, even in a sealed VRLA/AGM battery, for example, the potentialfor dryout is present, and a potential thermal runaway could occurbecause of water loss. Thus, it can be said that various known and/oralready-developed methods of combatting water loss in lead acidbatteries may provide little reduction in water loss and may requirehigh costs that may not match the value brought forth by variousdeveloped methods.

As such, there is clearly a need to develop lead acid batteries withimproved water loss performance, and/or the ability to reduceevaporation and/or electrolysis of water in the electrolyte of a floodedlead acid battery, that is cost effective.

The instant disclosure is designed to address at least certain aspectsof the problems or needs discussed above.

SUMMARY OF THE INVENTION

In accordance with at least selected embodiments, aspects, or objects,the instant disclosure or invention may address the above mentionedneeds, issues and/or problems, and/or provides or is directed to new orimproved vapor pressure barriers for lead acid batteries as well asvarious battery separators for lead acid batteries, and/or lead acidbatteries and related products, devices or vehicles comprising such leadacid batteries with such vapor pressure barriers, systems, relatedmethods, and/or the like. In general, the instant disclosure providesnew or improved lead acid battery vapor pressure barriers and/or methodsof manufacture and/or use thereof. In at least select embodiments, theinstant disclosure provides a new or improved lead acid battery with avapor pressure barrier and/or a material or battery separator thatreduces the water loss from the battery. In one embodiment, a method ofreducing the water loss of a lead acid battery may include providing avapor pressure barrier inside the lead acid battery anywhere between theexternal environment and the electrolyte within the battery.

The instant disclosure or invention is directed to new or improved leadacid batteries and components therefor, vapor pressure barriers,separators, systems, devices, products, vehicles, and/or related methodsof production and/or use thereof, and to various vapor pressure barriersand/or systems of combinations of vapor pressure barriers and/orseparators for use in a lead acid battery, and to batteries and/orvehicles including such vapor pressure barriers, systems, batteries, orcombinations thereof. In at least select embodiments, the instantdisclosure or invention is directed toward a new or improved vaporpressure barrier or barriers, sometimes in conjunction with improvedbattery separators, for lead acid batteries and related products,devices or vehicles including such batteries, and/or methods forcreating such vapor pressure barriers and/or battery separators. In atleast select embodiments, the instant disclosure or invention relates tonew or improved lead acid batteries and vehicles, and/or methods ofmanufacture and/or use thereof for enhancing the water loss performanceof the lead acid battery, which battery may be in a particular system,device or vehicle.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 includes a graph showing the reduction in water loss forbatteries incorporating one or more vapor pressure barriers according tovarious embodiments, aspects or objects of the invention describedherein.

DETAILED DESCRIPTION OF THE INVENTION

The instant disclosure provides various vapor pressure barriers for alead acid battery and a lead acid battery having one or more of suchvapor pressure barriers as well as various battery separators insidelead acid batteries, and various improved batteries inside improvedvehicles comprising the same. The vapor pressure barriers describedherein may be for reducing water loss (typically water vapor) from thelead acid battery. As such, the instant disclosure provides a lead acidbattery with reduced or improved water loss. Reducing and/or improvingwater loss, as used herein, means less water is lost from the batteryover time compared with previously known batteries. By way of example,FIG. 1 (described in more detail below) provides such an example ofreduction in water loss for lead acid batteries employing a batteryseparator and/or a vapor pressure barrier according to variousembodiments described herein.

The various vapor pressure barriers for a lead acid battery of theinstant disclosure may provide reduced and/or improved water loss (areduction in the amount of water lost over typical batteries) by any oneor more of the listed approaches or means in a lead acid battery. Inselect embodiments, the vapor pressure barrier may provide additionalsurface area for coalescing of vapor and/or mist. In still otherembodiments, the vapor pressure barrier may act as a de-mister forvapor, mist, fog, and/or droplets trying to escape from the lead acidbattery and create water loss. In select embodiments, the vapor pressurebarrier may provide a tortuous path for H₂ and O₂ gases to escape. Inselect embodiments, the vapor pressure barrier may provide a means ofbringing catalytic options for H₂/O₂ recombination. In selectembodiments, the vapor pressure barrier may provide a means of reducingvapor carried out of the battery during overcharge or periods ofintentional or unintentional gassing. In select embodiments, the vaporpressure barrier may reduce the non-isopiestic (or non-equal pressure)tendency of the lead acid battery to have uneven electrolyte levelsamong battery cells. By way of example, in some lead acid batteries,water vapor may go from one cell to another such that the electrolytelevel in one cell of the battery is higher than in another cell of thebattery, which is undesirable and may lead to strong/weak sister cellsin the battery and could reduce battery life, capacity and powerdelivery through, for example, grid corrosion, corrosion of top lead orthe conductive lead above the electrolyte level, which could lead tocell failure or dead cells, and so forth.

The vapor pressure barrier for a lead acid battery of the instantdisclosure may be provided in many positions and/or locations forreducing and/or improving water loss of the battery. In selectembodiments, the vapor pressure barrier may be positioned between theoperating electrolyte and the external atmosphere. In selectembodiments, the vapor pressure barrier may be positioned in the headspace of the battery. In select embodiments, the vapor pressure barriermay be positioned in contact with the electrolyte. In other selectembodiments, the vapor pressure barrier may be positioned within theelectrolyte.

The vapor pressure barrier for a lead acid battery of the instantdisclosure may be any material for reducing and/or improving the waterloss of the lead acid battery. In select embodiments, the vapor pressurebarrier may include any material of suitable density that will float ontop of the electrolyte, have low solubility in the electrolyte and/orremain flowable/pourable over the operating temperatures of the battery.

And such vapor pressure barrier or barriers may be, according to thisinvention, used in conjunction with a battery separator designed to haveimproved water loss features of its own. For example, various batteryseparators may be used in flooded lead acid batteries that include, forinstance, various polyethylene battery separators, particularly thoseknown and commercially available from Daramic, LLC. To improve the waterloss performance of a battery incorporating such a battery separator,such a polyethylene battery separator may be coated with a material thatprovides for unexpected improvement in water loss performance for aflooded lead acid battery. Such materials include the materialsdescribed in, for example, U.S. Patent Publication No. 2012/0094183,which is hereby incorporated by reference in its entirety.Alternatively, such materials may include the materials described in,for example, U.S. Provisional Patent Application Ser. No. 62/121,120filed Feb. 26, 2015, and the related non-provisional U.S. patentapplication Ser. No. 15/054,504 filed Feb. 26, 2016, which is beingfiled concurrently herewith, both of which are hereby incorporated byreference in their entireties. Thus, in various embodiments of thepresent invention, a synergistic and unexpected level of water lossimprovement may result from providing a lead acid battery thatincorporates an improved battery separator as well as one or more vaporpressure barriers somewhere between the external environment and theelectrolyte and/or somewhere within the electrolyte within the battery.

In select embodiments, the vapor pressure barrier for a lead acidbattery according to the instant disclosure may include an oil layer. Inselect oil layer embodiments, the oil may be some sort of mineral oil,for example, a white mineral oil. In various embodiments, the oil layermay be modified by adding electrolyte soluble components that are mobileinto the electrolyte phase to provide additional benefit by means ofincreasing the electrochemical overpotential value which is responsiblefor gas evolution in the cell. Said synergistic components may beinorganic salts such as zinc sulfate, bismuth-containing compounds,various nonionic organic compounds including surfactants, naturallyderived or synthetically derived liquid polymeric compounds, oxygenatedpolymers, PPO (polypropylene oxide), PEG/PEO/POE (polyethylene glycol),oxygenated oils, water soluble polymers, and/or materials such as thosedescribed in U.S. Pat. No. 2,938,887, which is hereby incorporated byreference in its entirety, oxidation products of cellulosic materialsand other organic and inorganic compounds having suitable solubility anddispersive properties in the aforementioned oil layer and having somedegree of solubility in the electrolyte thus portioned wholly orpartially within the oil and/or electrolyte phases. In one particularexample, PVA or polyvinyl acetate, or some other material such as anencapsulation material may be used as a delivery method or system forproviding one or more oil as a vapor pressure barrier to the floodedlead acid battery such that the PVA outer layer or shell orencapsulation material disintegrates in the electrolyte (is soluble inthe electrolyte) and the oil remains to serve as a vapor pressurebarrier or part of a vapor pressure barrier.

The oil layer may be any of various oil layers, including, but notlimited to, naturally or synthetically derived oils, and/or paraffinic,naphthenic, PAO, polyester functionalities among other natural base andblended oils and synthetic oils including oils formulated from naturalgas, and other petroleum gases. In various embodiments, the oil or oilsused as part of a vapor pressure barrier according to this invention maybe selected on the basis of insolubility in the electrolyte. Inaddition, selection of one or more oils to operate in a vapor pressurebarrier according to this invention includes taking into accountviscosity properties of the various oils which may allow for easyaddition to the battery under extremes in climate. In addition, theselection of various oils for use as part of a vapor pressure barrier inthe present invention further includes selecting oils which may be knownto be stable and/or resistant to oxidative attack and may contain, forexample, only small quantities of byproducts from refining. In addition,the selection of various oils to use as part of a vapor pressure barrieraccording to the present invention may include selecting one or moreoils which have been demonstrated to be electrochemically compatible bymeans of cyclic voltammetry analysis. Examples of such oils may include,but are not limited to, those utilized in the transformer, turbinepower, consumer products and biomedical industries.

In select embodiments, the vapor pressure barrier for a lead acidbattery according to the instant disclosure may include a nonwovenlayer. In select nonwoven layer embodiments, the nonwoven layer may bepositioned above the electrolyte. In other nonwoven layer embodiments,the nonwoven layer may be positioned within the electrolyte. In somenonwoven layer embodiments one or more oils as discussed above may beapplied on such a nonwoven layer. In other nonwoven layer embodiments,one or more oils as discussed above may be contained within such anonwoven layer. In various embodiments, the nonwoven may contain oilthat does not completely saturate the pores but instead spreads over thesurface of such a nonwoven to allow for repelling the gas mist.

In other select nonwoven layer embodiments, the nonwoven layer may beapplied over the headspace. In other select nonwoven layer embodiments,the nonwoven layer may be attached to the battery lid, for example, itmay be insert molded into such a lid or around the periphery of the ventorifices on the bottom of such a lid. In other select nonwoven layerembodiments, the nonwoven layer may be assembled as discrete piecesapplied inside the headspace of each cell during assembly. In otherselect nonwoven layer embodiments, the nonwoven layer may be assembledbetween the battery lid and the case. The nonwoven layer of the vaporpressure barrier may be any nonwoven layer. In select nonwovenembodiments, the nonwoven layer may include synthetic fibers, a glassmat, a melt stable nonwoven, a blended nonwoven, the like, othernonwoven, woven, or material layers that provide a vapor pressurebarrier, and/or combinations thereof. In select embodiments, the vaporpressure barrier for a lead acid battery according to the instantdisclosure may include a porous membrane such as a thin, flat, porous ormicroporous polymeric membrane or mat (such as a filled or unfilledmicroporous polyethylene membrane or mat). Positioning of such a porousmembrane may vary in the same ways described above as for a nonwovenlayer.

In select embodiments, the vapor pressure barrier for a lead acidbattery according to the instant disclosure may include a catalyst. Thecatalyst may be any catalyst for reducing and/or improving water loss ofthe lead acid battery. In select embodiments the catalyst may promoteO₂/H₂ recombination with the driving force of energetically favorablewater formation. Thus water may be cycled (water>gas>water>gas> . . . )over the cycle life of the battery resulting in highly optimal waterloss conditions. The catalyst may include one or more materials that maybring about the addition of atomic oxygen to atomic hydrogen toefficiently achieve the condensation to liquid water. Preferredcatalytic choices may include those materials which react efficiently toform water in low-pH oxidative environments. The substrate platform forcatalytic recombination can be synthetic nonwoven material, variousporous membranes stable to the battery environment, and/or the batterycase, for example, the top of the case and the venting structurescomprised within the case. By way of example only, vapor deposition ofplatinum on a membrane or fibrous structure could provide a vaporpressure barrier for use within a flooded lead acid battery.

A lead acid battery may be provided, made or manufactured according tothe instant disclosure with any of the various embodiments of the vaporpressure barrier and/or separators as shown and/or described herein. Thelead acid battery, like a flooded lead acid battery, or an EFB, may beimproved with any of the various embodiments of the vapor pressurebarrier and the various battery separators as shown and/or describedherein. The improvements of the lead acid battery with any of thevarious embodiments of the vapor pressure barrier and battery separatorsas shown and/or described herein may include, but are not limited to,having reduced and/or improved water loss. Although a flooded lead acidbattery or an enhanced flooded battery may be the preferred batteries,other batteries may benefit from the inventive barriers and/orseparators. For example, automotive, deep cycle or industrial batteries,VRLA, AGM, VRLA AGM, gel electrolyte, and/or the like. Also, deep cyclebatteries used for various industrial applications, mining equipment,golf cars, and other applications, particularly those where periodicovercharge is required, and stationary applications requiring constantovercharge, may also benefit from reduced water loss technologies. Suchbatteries or systems, and other batteries or systems, will see areduction in required maintenance, less frequent watering required,and/or longer service life, even in cases of irregular maintenanceschedules.

The instant disclosure also provides a method of reducing water loss ofa lead acid battery. The method may include providing a vapor pressurebarrier according to any of the various embodiments shown and/ordescribed herein. In select embodiments, the method of reducing waterloss of a lead acid battery may include reducing vapor loss from thevented lead acid battery. In select embodiments of the instant method ofreducing water loss of a lead acid battery, the vapor pressure barriermay be provided between the operating electrolyte and the case and/orthe external atmosphere. In select embodiments of the instant method ofreducing water loss of a lead acid battery, the vapor pressure barriermay: provide additional surface area for coalescing of vapors; provide atortuous path for H₂ and O₂ gases to escape; provide a means of bringingcatalytic options for H₂/O₂ recombination; provide a means of reducingvapor carried out of the battery during overcharge or periods ofintentional or unintentional gassing; reduce the non-isopiestic tendencyof the lead acid battery to have uneven electrolyte levels which leadsto strong/weak sister cells and reduces life, capacity and powerdelivery through grid corrosion, corrosion of top lead, and/orcombinations thereof.

In one particular embodiment of the present invention, a battery havingimproved water loss characteristics is produced by creating a physicalvapor pressure barrier between the electrolyte and the head space of thebattery. In such an embodiment, the water loss reduction compared withcontrol batteries may be more than a 25% reduction in water loss, insome embodiments, more than a 35% reduction in water loss, in still someembodiments, more than a 45% reduction in water loss, and in someembodiments, more than a 55% reduction in water loss compared withcontrol batteries. In such embodiments, a battery system may be createdincluding an improved battery separator including, for example, apolyethylene battery separator coated with a material specificallydesigned for improving water loss characteristics of a battery (such asa material more fully described in U.S. Patent Publication No.2012/0094183, incorporated by reference herein); then, addingelectrolyte to the battery; and then, adding a layer of oil above theelectrolyte to serve as a vapor pressure barrier for the battery system.In various embodiments, up to 5 mL of oil per battery cell is added tocreate such a battery; in other embodiments, up to 10 mL of oil perbattery cell is added; in still other embodiments, up to 30 mL of oilper battery cell is added; in other embodiments, up to 60 mL of oil perbattery cell is added.

Examples

Various laboratory assembled batteries were created to determine thelevel of water loss improvement the battery experienced using variousembodiments of the present invention. Various batteries were assembledin a lab using battery separators commercially available from Daramic,LLC and then creating a vapor pressure barrier in conjunction with theuse of such a separator. FIG. 1 illustrates a bar graph of water loss ingrams of weight loss over a 21 day overcharge at 2.4 Volts/cell (14.4Volts total for a 6-cell, 12-Volt battery) for various laboratoryassembled batteries with vapor pressure barriers according to selectembodiments of the instant disclosure. These were vented batteries in a60° C. water bath. The battery with a control polyethylene separator,commercially available from Daramic, LLC and containing various waterloss additive(s), as the battery separator is used for reference as acontrol. Then, two batteries were assembled using a vapor pressurebarrier, one with a layer of Oil A, and one with a layer of Oil B. Theresults show an unexpectedly high level of water loss reduction whencombining the water loss technology of an enhanced battery separatorwith the water loss technology of an improved vapor pressure barrier forthe system. By way of example, the system with the control polyethylenebattery separator revealed water loss in grams of between 150 and 200grams, whereas the systems with a layer of oil reduced that water lossdown to under 100 grams over the period of overcharge. Also, it isbelieved that the unexpected improvement in water loss results wouldalso be high and unexpected relative to a standard polyethylene batteryseparator with an oil layer but without a coating of or the addition ofa water loss additive (such as the additive(s) associated with theDaramic polyethylene battery separator used as the control in the graphof FIG. 1). Thus, with the present invention, one important water lossimprovement technology, improving it by adding physical vapor pressurebarrier(s) to the system, is combined with another important water lossimprovement technology, improving it by adding an improved batteryseparator (for example, a coated separator or a separator including oneor more novel additives for reducing water loss in a flooded lead acidbattery system), with potentially synergistic and unexpected results.

In accordance with at least certain embodiments, aspects or objects, newor improved lead acid batteries with vapor pressure barriers and/orimproved battery separators, systems, and/or methods of manufactureand/or use thereof are contemplated, provided or disclosed. In at leastselect embodiments, the instant disclosure provides new or improved leadacid batteries with a vapor pressure barrier or system. In at leastselect embodiments, the instant disclosure provides new or improved leadacid battery vapor pressure barriers along with new or improved batteryseparators, and/or methods of manufacture and/or use thereof. In atleast select embodiments, the instant disclosure provides a new orimproved lead acid battery with a vapor pressure barrier that reducesthe water loss from the battery. In at least select embodiments, amethod of reducing the water loss of a lead acid battery may includeproviding a vapor pressure barrier, such as a layer of oil, inside thelead acid battery along with an improved battery separator.

In at least select embodiments, aspects or objects, the presentdisclosure or invention may address the above needs, and/or may provideor be directed to new or improved lead acid batteries and componentstherefor, vapor pressure barriers, separators, systems, vehicles, and/orrelated methods of production and/or use thereof, and to various vaporpressure barriers and/or systems of combinations of vapor pressurebarriers and separators for use in a lead acid battery, and to batteriesand/or vehicles including such vapor pressure barriers, systems orcombinations. In at least select embodiments, the instant disclosure orinvention is directed toward a new or improved vapor pressure barrier orbarriers, sometimes in conjunction with improved battery separators, forlead acid batteries and related products, devices or vehicles includingsuch batteries, and/or methods for creating such vapor pressure barriersand/or battery separators. In at least select embodiments, the instantdisclosure or invention relates to new or improved lead acid batteriesand vehicles, and/or methods of manufacture and/or use thereof forenhancing the water loss performance of the lead acid battery, whichbattery may be in a particular system, device or vehicle.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicating the scope of the invention.Additionally, the invention illustratively disclosed herein suitably maybe practiced in the absence of any element which is not specificallydisclosed herein. Many other modifications and variations of the presentinvention are possible to the skilled practitioner in the field in lightof the teachings herein. It is therefore understood that, within thescope of the claims, the present invention can be practiced other thanas herein specifically described.

1-15. (canceled)
 16. A battery separator comprising an oil layer on aporous membrane or mat, wherein the oil layer comprises one or moreselected from the group consisting of naturally derived oils andsynthetically derived oils.
 17. The battery separator of claim 16,wherein the oil layer comprises a paraffinic oil.
 18. The batteryseparator of claim 16, wherein the oil layer comprises a napthenic oil.19. The battery separator of claim 16, wherein the oil layer comprises apolyalphaolefin (PAO) oil.
 20. The battery separator of claim 16,wherein the oil layer comprises an oil with polyester functionalities.21. The battery separator of claim 16, wherein the oil layer comprises amineral oil.
 22. The battery separator of claim 21, wherein the oillayer comprises white mineral oil.
 23. The battery separator of claim16, wherein the oily layer comprises two or more naturally derived oils,two or more synthetically derived oils, or a mixture of at least onenaturally derived oil and at least one synthetically derived oil. 24.The battery separator of claim 16, wherein the oil layer furthercomprises one or more selected from the group consisting of zincsulfate, low HLB surfactants, and other materials that reduce waterloss.
 25. The battery separator of claim 24, wherein the oil layerfurther comprises zinc sulfate.
 26. The battery separator of claim 24,wherein the oil layer further comprises one or more low HLB surfactants.27. The battery separator of claim 24, wherein the oil layer furthercomprises one or more other materials that reduce water loss.
 28. Thebattery separator of claim 16, wherein the oil layer is provided on aporous membrane.
 29. The battery separator of claim 28, wherein theporous membrane is microporous.
 30. The battery separator of claim 28,wherein the porous membrane is a filled or unfilled polyethylene porousmembrane.
 31. The battery separator of claim 16, wherein the oil layeris provided on a porous mat.
 32. The battery separator of claim 31,wherein the porous mat is microporous.
 33. The battery separator ofclaim 31, wherein the porous mat is a filled or unfilled polyethyleneporous mat.
 34. A lead acid battery comprising the battery separator ofclaim 16, wherein the lead acid battery exhibits low or reduced waterloss.
 35. A lead acid battery comprising the battery separator of claim24, wherein the lead acid battery exhibits low or reduced water loss.